Conventional vascular grafts have long been used for vascular repair in humans and animals. These devices are typically flexible tubes of woven or knitted polyethylene terephthalate or porous polytetrafluoroethylene (hereinafter PTFE). Grafts of biological origin have also been used, these being typically fixed human umbilical or bovine arteries. Such conventional vascular grafts usually require invasive surgical methods that expose at least both ends of the segment of the vessel to be repaired. Frequently it is necessary to expose the entire length of the vessel segment. These types of repairs cause major trauma to the patient with corresponding lengthy recovery periods and occasionally, even death.
Alternative methods have evolved which use intraluminal vascular grafts in the form of adjustable stent structural supports, tubular grafts, or a combination thereof. These devices are preferably remotely introduced into a body cavity by the use of a catheter type of delivery system. Alternatively, they may be directly implanted by invasive surgery. The intent of these methods is to maintain patency after an occluded vessel has been re-opened using balloon angioplasty, laser angioplasty, atherectomy, roto-ablation, invasive surgery, or a combination of these treatments.
Intraluminal vascular grafts can also be used to repair aneurysmal vessels, particularly aortic arteries, by inserting an intraluminal vascular graft within the aneurysmal vessel so that the prosthetic device withstands the blood pressure forces responsible for creating the aneurysm. In addition, intraluminal vascular grafts provide a new blood contacting surface within the lumen of a diseased living vessel.
If the intraluminal graft used has a thin enough wall and adequate flexibility, it may be collapsed and inserted into a body conduit at a smaller diameter and at a location remote from the intended repair site. A catheter type of delivery system is then used to move the intraluminal graft into the repair site and then expand its diameter appropriately to conform to the inner surface of the living vessel. Various attachment methods including the use of adjustable stents may be used to secure the intraluminal graft at the desired location without the necessity of invasive surgery.
Stent grafts (or covered stents) have been used extensively where external support, such as in the form of rings, spirals, or metal frames with a multiplicity of openings, and the like are required when the application or patient anatomy may exert forces that either could crush or collapse the intraluminal device were it not for the presence of the support. A support is also required in situations where the internal pressure on the device would result in undesirable diametric growth of the device were it not for the presence of the support. Stent grafts can take many forms and may be constructed of a wide variety of materials including, but not limited to, stainless steel, tantalum, nitinol stent materials and polyurethane, ePTFE, and Dacron cover materials.